Appearance

Steatornis caripensis is a large (41-49 cm) nocturnal bird. Oilbirds look like overgrown nightjars. They are rufous brown and have white-spotted plumage; prominent rictal bristles; a heavy hooked bill; and eyes that are brown but reflect red. No differences have been reported geographically. Sexual dimorphism is slight, however, males are grayer and slightly larger than females.

There is no closely related species of Oilbirds as they are the sole living members of the family Steatornithidae (see Fossil History). As such, their closest relatives are other caprimulgiform birds (Caprimulgidae, Nyctibiidae, Podargidae, Aegothelidae) and birds of the order Apodiformes (Hackett et al. 2008, Mayr 2010).
Oilbirds resemble an overgrown nightjar. Their vocalizations, large size, and white-spotted plumage distinguish Oilbirds from potoos (Nyctibius) and nightjars (Hilty and Brown 1986, Hilty 2003).

Looks like a big nightjar. Heavy hooked bill, prominent. Eyes large, dark and reflect bright red. Above rufous brown, below paler and more cinnamon. Has smaller diamond-shaped white spots on head and underparts. Head is hawk-like. Crown has a few white dots (Hilty and Brown 1986, Hilty 2003). Wings are long, broad, and highly slotted. Wing-load is low (Bosque 2002). The tail is long and faintly barred black. While resting tail feathers form a tent-like inverted V, with the central feathers held higher and the outer feathers held lower. Legs are short and placed far forward so that at rest the head is held lower than the tail. Rictal bristles are prominent as in other Caprimulgiformes (Bosque 2002). Plumage dimorphism is subtle but males are grayer than females (Hilty and Brown 1986). They are also slightly larger (Bosque 2002). In flight note long and narrow wings (Hilty 2003).

Wing molt in early December and body molt in early April (Willard et al. 1991)

Iris: Dark brown but reflects bright red (Hilty and Brown 1986, Willard et al. 1991).

Bill: Brown (Field Museum of Natural History), reddish brown (Willard et al. 1991).

Tarsi and toes: Pink, hazel, light violet and pinkish flesh (Field Museum of Natural History, Willard et al. 1991).

Total length: 43-49 cm (Bosque 2002).

Wingspan: 95-107 cm (Bosque 2002).

Adult body mass: Males: 390.0 g, Females:360.0 g (Willard et al. 1991)